求高手！！！

function define() {
            var salesLabel = $("#SalesLabel").val();
            var profitLabel = $("#ProfitLabel").val();
            var firstSalesTextBox = $("#FirstSalesTextBox").val();
            var secondSalesTextBox = $("#SecondSalesTextBox").val();
            var thirdSalesTextBox = $("#ThirdSalesTextBox").val();
            var fourthSalesTextBox = $("#FourthSalesTextBox").val();
            var allSales = parseInt(firstSalesTextBox) + parseInt(secondSalesTextBox) + parseInt(thirdSalesTextBox) + parseInt(fourthSalesTextBox);
            var firstProfitTextBox = $("#FirstProfitTextBox").val();
            var secondProfitTextBox = $("#SecondProfitTextBox").val();
            var thirdProfitTextBox = $("#ThirdProfitTextBox").val();
            var fourthProfitTextBox = $("#FourthProfitTextBox").val();
            var allProfit = parseInt(firstProfitTextBox) + parseInt(secondProfitTextBox) + parseInt(thirdProfitTextBox) + parseInt(fourthProfitTextBox);
            if (firstSalesTextBox == "" || secondSalesTextBox == "" || thirdSalesTextBox == "" || fourthSalesTextBox == "" || firstProfitTextBox == "" ||
               alert("内容不能为空,请重新输入！"); 
          当我想在这输入为空后，直接跳到firstSalesTextBox 怎么写？}
            
            if (firstSalesTextBox < 0 || secondSalesTextBox < 0 || thirdSalesTextBox < 0 || fourthSalesTextBox < 0 || firstProfitTextBox < 0 ||
            secondProfitTextBox < 0 || thirdProfitTextBox < 0 || fourthProfitTextBox < 0) {
                alert("输入错误，请重新输入");
                return false;
            }            if (allSales <= 0 || allProfit <= 0) {
                alert("输入错误，请重新输入");
                return false;
            }
            else if (allSales < salesLabel || allProfit < profitLabel) {
                alert("输入错误，请重新输入");
                return false;
            }
        }